The following relates to the medical imaging and environmental isolation arts, and is described with example reference to medical imaging systems for imaging subjects in contained BioSafety Level 4 (BSL-4) environments. The following finds more general application in medical imaging or other diagnostics performed in conjunction with isolation environments for researching, processing, or otherwise manipulating or containing subjects exposed, or potentially exposed, to radioactive, toxic, biologically infectious, or other hazardous substances. It further finds application in medical imaging in conjunction with performing medical imaging or other diagnostics in isolation environments such as clean rooms, sterile rooms, inert gas environments, and so forth, that are controlled to limit contamination from normal environmental conditions.
Biologically hazardous and highly contagious diseases are an increasing public health concern. Increasing air travel promotes the rapid worldwide spread of contagions. Bioterrorism is another potential route to public exposure to hazardous contagions. Effective response to an outbreak of a contagion is facilitated by knowledge of the infectious agent (that is, the type or species of virus, bacterium, prion, spore, or so forth), effect of counteragents (such as drugs or other types of treatment), transmission pathways (such as airborne transmission, contact transmission, or so forth), incubation period before symptoms arise, and so forth. This knowledge is gained by suitable laboratory studies.
Medical imaging systems, such as magnetic resonance (MR) scanners, transmission computed tomography (CT) scanners, positron emission tomography (PET) scanners, gamma cameras for single-photon emission computed tomography (SPECT), and so forth are powerful tools in detecting physiological manifestations of diseases caused by hazardous contagions, exposure to radioactivity or toxic substances, and so forth. For example, such imaging techniques can detect malignant tumors or other abnormalities that may be indicative of infection or disease. Medical imaging techniques can be applied periodically (for example on an hourly, daily, weekly, or other basis) to image live human or animal subjects so as to track the progression of physiological response to the disease or to exposure to a radioactive or toxic agent. Techniques such as multi-nuclear MR spectroscopy can track metabolic changes associated with the disease progression. These medical imaging-based diagnostics are merely illustrative examples.
Although the benefits of medical imaging systems are well recognized, applying medical imaging systems in the context of an isolation environment has heretofore been difficult. The National Institute of Health (NIH) and Center for Disease Control (CDC) have promulgated operational criteria for laboratories conducting biological research into hazardous contagions. Four levels of isolation have been defined: BioSafety Level 1 (BSL-1), BSL-2, BSL-3, and BSL-4, with the level of isolation increasing with increasing BSL level. The BSL-3 level requires isolation steps such as physical separation of the laboratory working area from access corridors and controlled air flow. BSL-4 requires an isolation zone (sometimes called the “hot zone”) with dedicated air flow. The isolation zone is a room, room partition, or building that is sealed off to prevent escape of airborne contagions, and laboratory personnel working within the hot zone wear sealed environmental suits, such as hazardous material (HAZMAT) suits, with self-contained breathing apparatuses. Laboratory personnel and any items that leave the isolation zone must pass through an airlock and undergo specified decontamination procedures before being admitted outside the BSL-4 environment. The isolation environment should be designed to minimize or eliminate sharp corners or features, and to minimize or eliminate fine operational features such as small fasteners, control buttons, or the like which are difficult to manipulate while wearing isolation suit gloves.
The BSL-4 environment is an example. Other isolation environments are used, for example to provide a sterile environment for drug development and testing, to provide isolation of toxic or radioactive materials, or so forth. These isolation environments impose similar constraints such as restricted movement of personnel and equipment, accommodation of limited manual dexterity of gloved or otherwise suited personnel, limiting sharp corners or features, or so forth.
Introducing a complex and sensitive medical imaging instrument such as an MR scanner, CT scanner, or so forth into an isolation environment is problematic. The medical imaging instrument typically includes hundreds, thousands, or more components, some of which are difficult to access to perform decontamination, and some of which may be made of materials that are incompatible with the decontamination procedures applicable in the isolation zone. For example, corrosive chemicals or heating that may be used in BSL-4 decontamination can damage sensitive components of a medical imaging instrument.
Contamination is also problematic for the subject table used to position the subject in the bore or other imaging volume of the medical imaging instrument. Because the infected or potentially infected subject is placed on the subject table, the subject table is frequently decontaminated. For example, in a BSL-4 environment such decontamination should typically include a wipe-down with decontaminant chemicals between subjects, and occasional more extensive decontamination procedures. The subject table should also provide a steady, level surface when inserted into the medical imaging instrument, which imposes mechanical constraints on the table design.
A further consideration is that the subject table is handled or manipulated by personnel working in the isolation environment each time a new subject is loaded into or unloaded from the medical imaging instrument. These personnel may not be radiologists trained in the operation of medical imaging instruments, and may not be skilled in routine table maintenance tasks. Moreover, personnel in isolation environments typically have reduced dexterity due to wearing gloves, HAZMAT suits, or so forth. Contact between the subject table and personnel in the isolation zone can be reduced or even eliminated by automating operations such as translation of the table into and out of the bore or imaging region of the medical imaging instrument, but at the expense of introducing additional mechanical parts which complicate decontamination and may lead to more frequent mechanical failures.